Impact of pericardial restraint on right atrial mechanics during acute right ventricular pressure load

Abstract

Optimization of right atrial (RA) mechanics is important for maintaining right ventricular (RV) filling and global cardiac output. However, the impact of pericardial restraint on RA function and the compensatory role of the right atrium to changes in RV afterload remain poorly characterized. In eight open-chest sheep, RA elastance (contractility) and chamber stiffness were measured (RA pressure-volume relations) at baseline and during partial pulmonary artery (PA) occlusion. Data were collected before and after pericardiotomy. With the pericardium intact and partial PA occlusion, RA elastance increased by 28% ( P < 0.04), whereas RA stiffness tended to rise ( P = 0.08). However, after pericardiotomy, there was a significant fall in both RA elastance (54%, P < 0.04) and stiffness (39%, P < 0.04), and subsequent PA occlusion failed to induce a change in elastance ( P > 0.19) or stiffness ( P > 0.84). After pericardiotomy, RA elastance and stiffness fell dramatically, and the compensatory response of the right atrium to elevated RV afterload was lost. The ability of the right atrium to respond to changes in RV hemodynamics is highly dependent on pericardial integrity.

Interatrial shunt for chronic pulmonary hypertension: differential impact of low-flow vs. high-flow shunting

“…Although the present study included a chronic surgical instrumentation to mimic CPH, it was designed to compare acute hemodynamic changes following interatrial shunting. Thus the analytic methods employed were not dependent on absolute volume measurements and were consistent with previous studies involving the RA (20). The authors considered the use of an adjustable device to create an atrial septal defect, which would have been more physiological.…”

“…RA contractile performance was assessed using the "atrial end-systolic" PV relationship (RA-ESPVR; chamber elastance), as previously described (8,20,1,13). Atrial end-systolic pressure (RAPA-ES) and volume (RA-VolA-ES) points were determined for each cardiac cycle during preload reduction, and, by least squares linear regression, a straight line was fitted to the following equation:…”

“…Static RA stiffness was defined as the slope of the "atrial end-diastolic" P-V relation (8,20). Atrial end-diastolic pressure (RAP A-ED) and volume (RA-VolA-ED) points were determined at the time of maximum RA volume (corresponding to tricuspid valve opening and the RAP V-wave) for each cardiac cycle during preload reduction.…”

“…Eight adult mongrel dogs of either sex (20 -25 kg) were anesthetized using a standard protocol, as previously described by our laboratory (8,9,20). A median sternotomy was performed, leaving the pericardium intact, and a 5-Fr pressure catheter (Access Technologies, Skokie, IL) was introduced into the right ventricular (RV) free wall through a purse string suture.…”

Reservoir and conduit function of right atrium: impact on right ventricular filling and cardiac output

“…The three components of atrial function are 1) reservoir function, storing blood when the tricuspid valve is closed and releasing stored blood when it opens; 2) conduit function, passive blood transfer directly from the coronary and systemic veins to the right ventricle when the tricuspid valve is open; and 3) booster pump function, atrial contraction in late diastole to complete ventricular filling (10,13,31). Previous studies have demonstrated that pathologically altered left atrial conduit-to-reservoir function is an important determinant of left heart function and can profoundly affect cardiac performance (2, 4, 14 -17, 30, 33, 34, 38), but studies examining right atrial (RA) reservoir and conduit function are limited.The mechanics of the right atrium are complex (5,8,24,26). In 1628, William Harvey was the first to identify the atrium as a "receptacle and store-house" and reported that the right atrium was "the first to live, and the last to die" (12).…”